Over the past twenty-five years rotary mowers particularly designed for grass mowing have generally replaced reel-type mowers for residential as well as most commercial grass mowing applications for a variety of reasons. Firstly, the front and rear wheel spacing reduces mower tilting--secondly, the vertical drive shaft from the mower directly to the blade eliminates the requirement for blade driving belts, pulleys or chains required in reel-type mowers--and thirdly, the blades have only two cutting edges that simplify the sharpening of the blade.
It is important for a healthy lawn that the grass clippings be collected because if not the clippings promote lawn thatching which is a layer of dead grass and other material that forms directly above the soil that inhibits the growth of new grass and the influx of nutrients. For this reason a variety of bagging attachments have been devised for these rotary blade walking mowers, and one that has found considerable commercial success in the 1970's up until the present time is referred to as a rear-bagging system or catcher. In the rear-bagging system, a chute, generally rigid plastic or metal, extends generally tangentially rearwardly and upwardly from the right side of the cup-shaped mower housing. A material receiving container, sometimes rigid plastic and sometimes a flexible knit or woven polyester material, is positioned between and below the mower handle bars almost entirely behind the mower housing. In some cases the grass bag is supported on a rigid cross member extending between the handle bars and in others special brackets are provided for this purpose. These rear-bagging containers have capacities between less than one bushel to up to approximately two bushels maximum. The maximum limit on the bag capacity is dictated by an acceptable reduction in maneuverability of the mower that results as the bag becomes filled with grass, particularly damp grass, and of course human operator strength.
The location of the material receiving and collecting container in these rear-bagging units beneath the handle bars and behind the housing detracts significantly from the maneuverability of the mower and also reduces the quality of mower cutting as the bag becomes filled. The decrease in maneuverability results from the tendency of the material container to swing laterally as the mower is maneuvered by the operator during turning, and also since the center of gravity of the grass bag or container is considerably behind the mower housing, it tends to pivot the front wheels upwardly about the axis of the back wheels as the bag becomes filled. Since the cutting in a rotary mower occurs at the forward end of the mower housing, a slight raising of the forward wheels, along with a raising of the blade as it passes the forward part of the housing, causes the grass to be periodically cut higher at the forward end in a very uneven fashion.
Many of these rear bagging systems have high lift discharge chutes in an effort to promote complete filling of the collecting container, because the lower the discharge chute enters the collecting container the more difficult container filling becomes. These high lift chutes are rigid, usually plastic, and extend rearwardly from the housing discharge opening in a generally tangential direction with respect to the housing and upwardly at angles between 30 and 45 degrees. Flow tests on these prior chutes indicate that most of the flow in these chutes occurs in the lower right quadrant of the chute (visualize the chute cross section as being divided by two perpendicular lines). Thus, these prior attempts at rapidly elevating the material have only been partly successful because flow in the upper part of the chute is relatively low, resulting in incomplete bag filling. Moreover, to effect good container filling, it is necessary that flow speeds in these chutes exceed 4,000 feet per minute, fpm. However, in these high lift chutes, flow exceeds 4,000 fpm only in the lower quadrant of the chute and the average flow integrated over the entire chute cross-section is considerably below 4,000 fpm, in fact as much as 30% less.
Attempts have been made to improve bagging and increase the capacity of the material receiving container in rotary walking mowers, but they have not achieved any significant commercial success. An example of such a grass catching system is shown in the Nolan U.S. Pat. No. 3,398,514 in which a rear-bagging grass container is shown that fits closely around the rear end of the motor. A discharge chute extends upwardly from the right side of the right rear of the mower housing up into and through the container itself. This design is unacceptable since the chute extends almost all the way through the grass bag, decreasing bag capacity and making bag removal difficult with excessive material spillage.
The Enters, et al U.S. Pat. No. 3,708,968 shows a top-bagging material collection system in which an upwardly opening bag, supported on the handle bars, receives material from the mower through a very long upwardly and rearwardly extending discharge chute that exits above the height of the handle bars. This arrangement places far too much weight behind the mower and grass-cutting quality would be reduced even more than in present-day rear-bagging units.
The Carpenter U.S. Pat. Nos. 3,958,40l and 3,961,467 show a similar rear-bagging system in FIG. 6 that has the same disadvantages described above with respect to the Enters Patent.
The Lane U.S. Pat. No. 3,971,198, the Evans U.S. Pat. No. 3,987,606, the Carpenter U.S. Pat. No. 4,054,023, the Leader U.S. Pat. No. 4,030,273 and the Thomas U.S. Pat. No. 4,158,280 all show mowers that are similar in arrangement to the Enters mower and have the same primary disadvantage of increasing the rear offset load on the mower that tends to raise the forward end of the mower and provide very poor quality cutting.
It is a primary object of the present invention to ameliorate the problems noted above in prior rotary walking motors.